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I really don't know how else to describe it. Car has no issues starting or running, but for about the last 2 months every time I cold start it, the engine makes a sharp, high-pitched noise like a sneeze.

Can anyone tell me what this is or why it's happening?

UPDATE:

Ok, I finally managed to record the noise. I realised in my attempts to record that it certainly does not happen "every time". It happens maybe one time in ten, and rarely on a cold start. More often than not, it happens after I've been driving for a while and then stop and start the engine.

Here's the link to the video. You can clearly hear the squawk just after it starts.

http://www.youtube.com/watch?v=UlqBFf63wXE

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Do you think you could record the noise? Sneeze and high-pitched are kind of ambiguous ways to describe engine noises... –  vlsd Nov 3 '13 at 22:15
    
yes, I'll record it today and edit my original post –  roryok Nov 4 '13 at 6:51
    
A "sneeze" usually means air is coming out of something it shouldn't. That means a crack in an air hose or a clamp that's not tight enough, or your turbo's plenum(or is it called a diaphragm?) may have a tear in it. But this is the first time I've heard about it happening on start-up. Best thing is to open the engine bay and record a video while someone else starts up the car. Also try to focus in on exactly where the noise is coming from as that will help isolate the cause. –  Juann Strauss Nov 4 '13 at 11:54
    
I tried recording the sound this morning but it didn't make it. I should explain this issue is intermittent. Frequent, but not constant. –  roryok Nov 4 '13 at 15:38
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2 Answers

up vote 5 down vote accepted

We have a Mk4 TDI Jetta that makes a sound after startup that might be described as a sneeze. I'm fairly confident that it's the starter motor's overrun clutch.

As soon as the engine "starts," it begins turning faster than the starter can turn. For this reason, starters have a one-way clutch, called an overrun or sprag clutch. This permits the starter to turn the engine, but prevents the engine from turning the starter, protecting the starter.

On my vehicle, I imagine there's some play or a worn bearing in this clutch, because as soon as the engine fires, there's a short (~1-2sec) buzzing noise that starts high in pitch and decreases in pitch quickly as the sound dies away. One might desribe this sound as "throat clearing" or "sneezing" in nature.

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I'm still trying to record it, as it tends to not happen when I have the camera on it (bloody typical). Mine lasts less than 1 second, and doesn't change pitch. It's probably better described as a kind of squawk like a chicken might make. I'll try and record it again this evening. –  roryok Nov 4 '13 at 15:40
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problem solved. turn on camera before starting car. –  mac Nov 4 '13 at 17:25
    
=) thanks mac, that seems to be working alright –  roryok Nov 5 '13 at 6:59
    
Have you checked the tension on your belts? A "squawk" could also be a belt slipping ;) –  Juann Strauss Nov 6 '13 at 9:13
    
@roryok I just watched your video. That's the same sound that I was describing. For what it's worth, ours has done this off-and-on for years now. It may grenade itself to pieces at some point, but so far so good. –  mac Nov 8 '13 at 15:14
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This is a noise typically Volkswagen. It is the startet motor. The starter motor extends into the bell housing of the gearbox. The extension on the starter acts as a support for the front of the starter motor. It runs in a bushing which becomes dry over time. You can either ignore it, or remove the starter motor and with a long artists brush and put copper based grease into the bush, then refit the starter. The noise is the starter slowing down and chattering in the bush.

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